The present invention relates generally to equipment utilized and operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides an electrical power generator.
Electrical power for use in a downhole environment has generally in the past been either stored in a device, such as a battery, and conveyed downhole or it has been transmitted via conductors, such as a wireline, from the surface or another remote location. As is well known, batteries have the capability of storing only a finite amount of power therein and have environmental limits, such as temperature, on their use. Additionally, batteries are not readily recharged downhole.
Electrical conductors, such as those in a conventional wireline, provide a practically unlimited amount of power, but require special facilities at the surface for deployment and typically obstruct the production flowpath, thereby preventing the use of safety valves, limiting the flow rate of fluids through the flowpath, etc., while the conductors are in the flowpath. Thus, wireline operations are typically carried out prior to the production phase of a well, or during remedial operations after the well has been placed into production.
In other circumstances, such as relatively permanent production situations, the conductors may be positioned external to a tubing string. For example, such external conductors have been used for powering and communicating with sensors in production situations. However, this makes running the tubing string very time-consuming and often results in unreliable electrical connections, etc.
What is needed is a new method of generating electrical power. The method should not require that power be stored in a device and then conveyed downhole or to another remote location where it is difficult to recharge. The method should also not require that power be transmitted from a remote location via one or more conductors positioned in a production flowpath of a well or external to a tubing string in the well. It is accordingly an object of the present invention to provide a new method whereby power is generated, and to provide an apparatus for such power generation.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a power generator and associated method are provided which solve the above problems in the art. The power generator operates by displacing a member thereof in response to pressure changes in the generator, for example, due to fluid flow through the generator. A piezoelectric material produces electricity when the member displaces. The power generator may be used in a downhole environment or in conjunction with fluid flow through any conduit.
In one aspect of the present invention, a power generator includes a fluid conduit and a piezoelectric material attached to the conduit. When a pressure change is experienced in the conduit, such as, due to fluid flowing through the conduit, the piezoelectric material produces electricity, due to flexing of the conduit. The conduit may include a reduced thickness portion, which has an increased degree of flexing in response to the fluid flow, with the piezoelectric material being attached to the reduced thickness portion.
In another aspect of the present invention, a power generator includes a mass reciprocably disposed relative to an outer housing of the generator. A bias member is positioned between the mass and a piezoelectric material. Fluid flowing through the housing causes the mass to displace and thereby induce strain in the piezoelectric material via the bias member. A fluid conduit may extend in the housing, with the mass, bias member and piezoelectric material being positioned between the conduit and the housing. Fluid flow through the conduit may be diverted to flow between the conduit and the housing.
In still another aspect of the present invention, a power generator includes a fluid conduit and a fluid chamber in fluid communication with the fluid conduit. The chamber vibrates in response to pressure changes in the conduit, such as, due to the flow of fluid through the conduit. A piezoelectric material attached to the chamber produces electricity when the chamber vibrates. The piezoelectric material may be attached to internal or external walls of the chamber, to a membrane bounding a portion of the chamber, or to a piston used to adjust a volume of the chamber.
In yet another aspect of the present invention, a power generator includes a fluid conduit and a member extending into a flow passage of the fluid conduit. The member vibrates in response to fluid flow through the fluid conduit. A piezoelectric material produces electricity in response to the vibration of the member. The member may extend generally transversely relative to the flow passage, and the piezoelectric material may support the member in position relative to the fluid conduit.
In a further aspect of the present invention, a power generator includes a fluid conduit and a member having an orifice formed therethrough. Fluid flowing through the fluid conduit also flows through the orifice, causing the member to vibrate. A piezoelectric material produces electricity when the member vibrates.
In a still further aspect of the present invention, a power generator includes a fluid conduit, a member displacing within the fluid conduit in response to fluid flow through the fluid conduit, a retainer preventing displacement of the member out of the fluid conduit, and a piezoelectric material producing electricity in response to displacement of the member. The member may be a sphere which is retained in an enlarged cavity in the fluid conduit. The piezoelectric material may be positioned between the member and the fluid conduit, or it may be positioned between the retainer and the fluid conduit, so that when the member contacts the retainer, strain is induced in the piezoelectric material.
In an additional aspect of the present invention, a power generator includes a fluid conduit having a flow passage formed therethrough and a cavity. A membrane separates the flow passage from the cavity. The membrane flexes in response to pressure changes in the flow passage, such as, due to fluid flow through the flow passage, and a piezoelectric material disposed within the cavity produces electricity in response to the membrane flexing.
In another aspect of the present invention, displacement of a member in response to fluid flowing through a flow passage is increased by inducing turbulence in the fluid flow. A fluid conduit through which the flow passage extends may be shaped to induce the turbulence, for example, by helically shaping the fluid conduit, or by helically forming a recess or protrusion internally or externally on the fluid conduit. Protrusions may also extend into the flow passage upstream of the member.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings.